As containers for containing various contents such as cosmetics, chemicals, foods and the like, containers having a resin layer on the inner side thereof have been conventionally used. The resin layer protects the container from the content contained therein. When the resin layer is formed on the inner surface of the container, for example, a coating material comprising a component obtainable by dispersing a resin in an aqueous medium (hereinafter referred to as “aqueous dispersion”) is used. The coating materials include a coating material comprising an aqueous dispersion of a polyolefin such as polyethylene etc. and the resin layer formed from the coating material has excellent flexibility, chemical resistance and other properties.
As containers having such a resin layer, for example, Patent document 1 discloses a tube-type container having a polyethylene-coating layer formed by spray coating a polyethylene aqueous dispersion on the most inner layer of an aluminum tube. However, forming the polyethylene aqueous dispersion requires addition of a surfactant in order to disperse polyethylene, which is hydrophobic, in water. The surfactant remains in the resin layer even after drying with heat because of low volatility thereof. The surfactant remained in the resin layer elutes from the resin layer to a content with the elapse of time and adversely affects the content. Furthermore, the coating material of a polyethylene aqueous dispersion is generally difficult to form a uniform resin layer and sometimes causes pinholes or bubbles in the resin layer. Moreover, conventional coating materials of a polyethylene aqueous dispersion having a high viscosity have a problem in paintability (handling properties) such that in performing coating with a spray method, a nozzle for injecting the coating material is easily clogged with the coating material. The resin layer formed by polyethylene, further, has low adhesion strength with containers made of aluminum etc. Sometimes, the resin layer is therefore peeled off and the containers are thereby corroded by the content.
Patent document 2 discloses that a dried coating film of a polyolefin resin dispersing aqueous solution is used as a under coating film for coating and the like. It also discloses that an ionomer resin is suitable as the above polyolefin resin, in order to improve the adhesion with metals. However, the resin layer formed from the ionomer resin generally has inferior chemical resistance and heat resistance and also has a problem of being easily corroded.
On the inner surface of an aluminum tube on the market, a resin layer formed from an epoxy compound is generally provided. Since the epoxy compound contains detrimental substances such as bisphenol A, which is one kind of endocrine disrupting chemicals, and the like, the detrimental substances eluted adversely affect on the content of the tube, in the case of eluting from the resin layer.